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Grade: 12
        Hot water cools from 60degree celcius to 50 degree celcius in the first 10 min and to 42 degree celcius in the next 10 min .The temp of the surrounding.
10 years ago

Answers : (2)

Ramesh V
70 Points

average temp. in first case = (60+50) /2 = 55 C

average temp. in second case = (50+42) /2 = 51 C

as frm law of cooling

dT/dt = -k(T-To )  where To is temp. of surrounding

case 1 : dT = 10 C and dt = 10 mins

so ,  1=-k(55-To )         ....(1)

case 2 : dT = 8 C and dt = 10 mins

so ,  0.8=-k(51-To )       .........(2)

From 1 and 2 , we have

Temp of surr. as 35 C


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10 years ago
Visalakshi Senthil Kumar
24 Points
Excuse sir I need to correct u in the second step ie., (50+42)/2=46 
So the room temp would be 10C    
dT/dt=0.8=-k (46-t)
dT2/dt2 =k (55-t)
Dividing them both we get
Therfore t=10
Answer by Aswath S, AECS PU College, Bangalore Fiitjee
Future IIT ian     ha ha ha
4 years ago
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